1. Field of the Invention
The present invention relates to a lens-fitted photographic film unit and more particularly to a lens-fitted photographic film unit having an improved kick-type shutter blade.
2. Prior Art
Lens-fitted photographic film units (hereinafter simply referred to as film units) are well known having a simple photograph-taking mechanism as disclose din U.S. Pat. No. 4,884,087. Such film units can be purchased nearly everywhere at low prices, making it possible to take photographs anywhere without carrying about heavy and expensive cameras.
Such a film unit has a main body with a taking lens, a shutter mechanism and a single-frame advancing mechanism, and front and rear covers. A 135-type photographic film cassette defined by ISO code 1007, 1979 version and a photographic film that has been drawn out of the photographic film cassette and wound in a roll are contained in the main body in a light-tight manner. Thus, the 135-type photographic film cassette used in the film unit can be subjected to photographic printing systems now in operation to obtain photoprints at low cost.
The thickness of the film unit is only slightly greater than the diameter of the photographic film cassettes, so as to render the unit more readily portable. However, there have been carried out studies to make the size of compact cameras approach the size of a credit card or a cigarette case. In this connection, it is desired to further miniaturize the film unit whilst still using a 135-type photographic film cassette.
There is disclosed a much more compact film unit with a 135-type photographic film cassette in U.S. application Ser. No. 07/928,703. In this film unit, the front outside surface of the film takeup chamber containing the cassette projects forward relative to the front outside surface of the film supply chamber. Correspondingly, a portion of the front cover follows the outline of the front outside surface of the film take-up chamber such that the projecting portion serves as a grip portion while the other portion of the front cover is flat and disposed rearwardly. The front cover is provided with a lens hood projecting therefrom in order to accommodate a taking lens and to dispose it at the same distance from the surface of the photographic film as in conventional film units.
Furthermore, a single kick-type shutter blade is used in order to permit manufacture of the film unit at low cost. The shutter blade is rotatably mounted on a flat shutter mount and has a claw portion and a masking portion for opening closing the shutter opening. Upon depression of a shutter release button, a shutter actuating lever is swung from a charge position into an initial position because of the force of a spring. At this time, the claw portion of the shutter blade is hit by the shutter actuating lever. Thereby, the shutter blade is swung against the force of a spring to open the shutter opening for an exposure. Instantly, the shutter blade is returned to the initial position owing to the force of the spring to terminate the exposure.
The shutter blade needs to be disposed directly behind the taking lens in order to prevent unevenness of exposure. Therefore, it is necessary to provide that the lens hood project not only in the region of the taking lens but also in the region wherein the shutter blade is swung. Besides, a gap is formed between the shutter blade and the shutter mount so as to make the shutter blade swing smoothly. However, in that case, there is a danger that external light can enter through the shutter opening through the gap. There has accordingly been suggested a shutter mechanism in which a projection is formed on a shutter mount so as to surround the shutter opening and cooperate with a projection formed on the rear side edge of the masking portion of the shutter blade to prevent external light from entering the shutter opening.
The shutter blade is attached to the shutter mount so as to leave a narrow gap between the shutter blade and the shutter mount. Then, if the rear surface of the masking portion is rough, it is rubbed by the projection of the shutter base plate due to ambient vibrations, which prevents smooth driving of the shutter blade. As a result, it is necessary to manufacture the shutter blade as accurately as possible, resulting in high cost of the product.